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chaloobi
SFN Regular
1620 Posts |
 Posted - 03/19/2008 : 07:09:20
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This is an interesting bit of research. In a nut shell, organisms tend to evolve toward greater complexity but almost never toward lesser complexity. Why would that be?
Life becomes more and more complex, evolution study finds Tue
WASHINGTON (AFP) - Life, as it evolves, becomes increasingly complex and rarely less so, a study of evolution by British and Canadian researchers has found.
In the study out Monday researchers looked back 550 million years in the fossil catalogue from today, checking several evolutionary branches of the crustacean family tree to see where animals evolved that became simpler than their ancestors.
But instead they found organisms that developed increasingly complicated structures and characteristics.
"If you start with the simplest possible animal body, then there's only one direction to evolve in, you have to become more complex," said Dr Matthew Wills from the Department of Biology & Biochemistry at the University of Bath who worked with colleagues Sarah Adamowicz from the University of Waterloo, Canada, and Andy Purvis from Imperial College London.
"Sooner or later, however, you reach a level of complexity where it's possible to go backwards and become simpler again," he said.
"What's astonishing is that hardly any crustaceans have taken this backwards route," added Wills. "Instead, almost all branches have evolved in the same direction, becoming more complex in parallel.
"This is the nearest thing to a pervasive evolutionary rule that's been found."
Adamowicz noted that "looking at many independent branches is similar to viewing multiple repeated runs of the tape of evolution.
"Our results apply to a group of animals with bodies made of repeated units. We must not forget that bacteria, very simple organisms, are among the most successful living things. Therefore, the trend towards complexity is compelling but does not describe the history of all life," she said. |
A couple thoughts:
#1. It seems like increased complexity is not necessarily the best way to go - doesn't more complexity mean more opportunities for things to go wrong? Shouldn't evolution prefer simplicity wherever possible?
#2. That said, the vast majority of organisms, like the trillion or so bacteria helping me digest my breakfast right now, are, and have remained for the history of life on Earth, very simple.
#3. But #2 isn't the same as going from simple to more complex back to simple again. They simply stayed fairly simple because increased complexity was not required for survival in perpetuity.
So does the increased complexity over decreased complexity rule stand? More research required? Assuming it does stand, anyone have any ideas why?
Link: http://news.yahoo.com/s/afp/20080318/sc_afp/usbiologycanadabritain_080318162118
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-Chaloobi
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filthy
SFN Die Hard
USA
14408 Posts |
Posted - 03/19/2008 : 07:45:55 [Permalink]
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I am not comfortable with this. It seems to assume that evolution has some sort of ingrained progression, which it does not. Evolutionary changes are triggered by the long-term enviornment. Some evolve in one direction, others in another, all at different rates. Should a species find itself in isolation from others of it's species, it will probably evolve into something related but different. And it could well begin to evolve into something less complex:
However, the genes for sight remain -- the kicker is that should sight return, it might not/probably won't be the same as what was there in the first place. Evolution might imitate itself, but seldom if ever, repeats itself.
So I ask: is a chicken more or less complex than a dromaosaur, remembering that chickens still have the genes to grow teeth?
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"What luck for rulers that men do not think." -- Adolf Hitler (1889 - 1945)
"If only we could impeach on the basis of criminal stupidity, 90% of the Rethuglicans and half of the Democrats would be thrown out of office." ~~ P.Z. Myres
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chaloobi
SFN Regular
1620 Posts |
Posted - 03/19/2008 : 08:04:52 [Permalink]
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Originally posted by filthy
I am not comfortable with this. It seems to assume that evolution has some sort of ingrained progression, which it does not. Evolutionary changes are triggered by the long-term enviornment. Some evolve in one direction, others in another, all at different rates.
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This has been my understanding as well. But the paper cited in the article seems to have found strong evidence, for crustaceans at least, that increased complexity is almost always favored over increased simplicity. Assuming the evidence is accurate and generally holds true for other groups then how can that be explained? |
-Chaloobi
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filthy
SFN Die Hard
USA
14408 Posts |
Posted - 03/19/2008 : 08:10:42 [Permalink]
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Originally posted by chaloobi
Originally posted by filthy
I am not comfortable with this. It seems to assume that evolution has some sort of ingrained progression, which it does not. Evolutionary changes are triggered by the long-term enviornment. Some evolve in one direction, others in another, all at different rates.
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This has been my understanding as well. But the paper cited in the article seems to have found strong evidence, for crustaceans at least, that increased complexity is almost always favored over increased simplicity. Assuming the evidence is accurate and generally holds true for other groups then how can that be explained?
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Goddidit!!
I dunno. I'm going to have to dig around a little.
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"What luck for rulers that men do not think." -- Adolf Hitler (1889 - 1945)
"If only we could impeach on the basis of criminal stupidity, 90% of the Rethuglicans and half of the Democrats would be thrown out of office." ~~ P.Z. Myres
"The default position of human nature is to punch the other guy in the face and take his stuff." ~~ Dude
Brother Boot Knife of Warm Humanitarianism,
and Crypto-Communist!
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recurve boy
Skeptic Friend
Australia
53 Posts |
Posted - 03/19/2008 : 08:21:31 [Permalink]
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Originally posted by chaloobi
#1. It seems like increased complexity is not necessarily the best way to go - doesn't more complexity mean more opportunities for things to go wrong? Shouldn't evolution prefer simplicity wherever possible?
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Evolution prefers advantages over disadvantages given some environment.
But something about moving to greater "complexity" makes sense.
Suppose you have the most basic organism. There is some random mutation or whatever. We now have something more complex than the most basic organism.
This new organism can mutate back, or have a different change occur. In the case of the backwards mutation, well, we already have that. We see no change. In the case where we have a different change, we now have a 3rd variation on the original organism.
So as evolution progresses, we must have more and more variations.
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pleco
SFN Addict
USA
2998 Posts |
Posted - 03/19/2008 : 08:28:17 [Permalink]
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| Perhaps complexity is an emergent property of evolution. |
by Filthy
The neo-con methane machine will soon be running at full fart. |
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Kil
Evil Skeptic
USA
13476 Posts |
Posted - 03/19/2008 : 08:35:03 [Permalink]
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| Would increased simplicity come with a decrease of genetic information? It looks like the answer is no, since that doesn't really happen, does it? If were talking about specialized increases to adapt to a changing environment, and those changes, like teeth, are lost due to later changes, and toothless beaks appear, is the animal any less complex? I don't see how it is. How are they looking at this is what I wonder? What criteria are they using to describe complexity? |
Uncertainty may make you uncomfortable. Certainty makes you ridiculous.
Why not question something for a change?
Genetic Literacy Project |
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marfknox
SFN Die Hard
USA
3739 Posts |
Posted - 03/19/2008 : 08:44:35 [Permalink]
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| Seems to me that increased complexity filled ecological niches which weren't there before. This would explain why the most simple organisms are still around and still very successful. Basically, life started simple 'cause that's how life starts, and then certain life forms that happen to become more complex survive because they fill niches which didn't exist before. And more and more niches get filled until the earth's carrying copacity maxes out. From that point on, all new life can only compete with already existing life since there would be no new territory. And at that point, things are so complex that evolving new features (which would make an organism more complex) are more likely to be an advantage. Thus, life tends to evolve toward increasing complexity. |
"Too much certainty and clarity could lead to cruel intolerance" -Karen Armstrong
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Ricky
SFN Die Hard
USA
4907 Posts |
Posted - 03/19/2008 : 09:27:39 [Permalink]
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| #2. That said, the vast majority of organisms, like the trillion or so bacteria helping me digest my breakfast right now, are, and have remained for the history of life on Earth, very simple. |
To think that bacteria today are the same as those which existed millions of years ago is rather unfounded. Just because they are still single cellular does not mean they don't have cool new proteins:
From http://www.edwardtbabinski.us/evolution/bacteria_evolution.html:
| The article also notes that microbes are champions at rapid evolution, and that new genes can jump between lineages, breaking the simple pattern of inheritance and allowing new genes and new proteins to sweep across a range of organisms. For example, chemists have developed new compounds, ever seen on earth before; weedkillers like atrazine and 2,4-D, or nitrotoluenes such as TNT. Yet in just a few decades new enzymes have evolved that are able break these chemicals down and even use them for food. |
Perhaps they are simple when compared to multicellular organisms, I know not how to compare the complexity of two different species let alone phylum. But one thing which we have great amount of evidence for is that they are more complex than they were in the past. |
Why continue? Because we must. Because we have the call. Because it is nobler to fight for rationality without winning than to give up in the face of continued defeats. Because whatever true progress humanity makes is through the rationality of the occasional individual and because any one individual we may win for the cause may do more for humanity than a hundred thousand who hug their superstitions to their breast.
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Ricky
SFN Die Hard
USA
4907 Posts |
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chaloobi
SFN Regular
1620 Posts |
Posted - 03/19/2008 : 09:49:32 [Permalink]
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Originally posted by Ricky
| #2. That said, the vast majority of organisms, like the trillion or so bacteria helping me digest my breakfast right now, are, and have remained for the history of life on Earth, very simple. |
To think that bacteria today are the same as those which existed millions of years ago is rather unfounded. Just because they are still single cellular does not mean they don't have cool new proteins:
From http://www.edwardtbabinski.us/evolution/bacteria_evolution.html:
| The article also notes that microbes are champions at rapid evolution, and that new genes can jump between lineages, breaking the simple pattern of inheritance and allowing new genes and new proteins to sweep across a range of organisms. For example, chemists have developed new compounds, ever seen on earth before; weedkillers like atrazine and 2,4-D, or nitrotoluenes such as TNT. Yet in just a few decades new enzymes have evolved that are able break these chemicals down and even use them for food. |
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I didn't say they were the same, but they have spent the last three billion years being simple organisms by comparison to multicellular organisms, or even eukaryotes for that matter.
| Perhaps they are simple when compared to multicellular organisms, I know not how to compare the complexity of two different species let alone phylum. But one thing which we have great amount of evidence for is that they are more complex than they were in the past. |
Yes, this discussion is quickly zeroing in on the key term here - what is this paper calling complexity? I think the answer is pretty clear cut when comparing a bacteria to a eukaryote or a multicellular organism. But what is more complex, a rat or a raccoon? A bear or a dog? A crab or a crayfish? |
-Chaloobi
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chaloobi
SFN Regular
1620 Posts |
Posted - 03/19/2008 : 09:55:55 [Permalink]
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Originally posted by Kil
Would increased simplicity come with a decrease of genetic information? It looks like the answer is no, since that doesn't really happen, does it? If were talking about specialized increases to adapt to a changing environment, and those changes, like teeth, are lost due to later changes, and toothless beaks appear, is the animal any less complex? I don't see how it is. How are they looking at this is what I wonder? What criteria are they using to describe complexity?
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I think you might be on to something here. If it's generally easier to add genetic information via mutation than to remove it, then that could be the answer. Or perhaps mutations that remove genetic information tend to be lethal more often than those that add. Or maybe there's an advantage to having lots of genetic information over having just a little - diversity on a genetic level within an individual having a similar benefit as species wide genetic diversity. This might explain why there's so much DNA that doesn't appear to have an actual function. (though hasn't there been some recent research suggesting the 'junk' DNA thought to make up the majority of the human genome is more functional than first thought?) |
-Chaloobi
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| Edited by - chaloobi on 03/19/2008 09:58:30 |
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filthy
SFN Die Hard
USA
14408 Posts |
Posted - 03/19/2008 : 12:30:55 [Permalink]
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I really don't think that crustation evolution ia all that good an an example. It is true that they have, for the most part, increased in complexity, blind cave and hydrothermal vent species being a expected exceptions. I think that arthropods in general should be included, and there we find quite an interesting story.
"Arthropods - The Origins of Life
There are over two million species of arthropods, who initially arrived on Earth in the middle of the Cambrian period. Naturally, they were more evolved than their ancestors in a variety of ways and thus possessed their own unique characteristics.
Essentially, arthropods are characterised by possessing jointed limbs and an exoskeleton. They are the most successful animal Phylum on the planet, in regards to population size and species diversity. There is thought to be over 2 million types of arthropod in today's world.
The exoskeleton may illustrate what life was like at the time. It is of a defensive, protective nature to possess a shell, thus this suggests that competition was quite fierce in the Cambrian era, both from parasites and potential predators.
The arthropods were also the first taxon of species to exhibit more advanced receptors in the form of eyes (photoreceptors) and the development of various chemoreceptors that could be used in both the external and internal environment. Such developments have naturally been advantageous over time, illustrated by ourselves.
Since the arthropods possessed such desirable features, their survival over the long term is apparent by their genetic diversity, elaborated upon below.
Crustaceans
As life originated in the sea, the sea was still a valuable ecological niche to the numerous species of the time. Crustacean means insect of the sea, and is a Subphylum of the Arthropoda Phylum.
Although abundant, the crustaceans remain relatively simple in the grand scheme of life, and thus did not diversify well in comparison to other organisms. Some of the species in this class were able to occupy the freshwater ecosystem over time, though not successful as what could have been. Competition from more adaptive organisms would have been a biotic factor here.
The continued use of feet was evident in these organisms, as a continuation of the organisms mentioned on the previous page of the timeline. The fact that the species' limbs were now jointed, they could move more flexibly and thus had an advantage.
Many crustaceans are herbivores, meaning they obtain food from the consumption of plants. They are of great importance to aquatic ecosystems, and are above species of phytoplankton (micro-scopic plants) in the food chain. This can be related to in the freshwater ecology tutorial investigating food chains and plankton.
Also, many crustacean animals feed on molluscs, the more evolutionary primitive animals mentioned on the previous page"
The argument can be made that, really, crustations have hit an evolutionary wall, of sorts. Due to their physical carecteristics, notably their exoskeletons, they are limited in diversity in size and even function. The largest known crustation is Macrocheira kaempferi, the giant spider crab. It can be as much as 9 to 12 feet in leg spread, but has a body the size if a large cantalope. It might weigh some 14 or 15 pounds. The Atlantic lobster can go as much as 40 pounds, or, I'm told, even more. Both of these animals are highly specialized, deep sea (but not bathypelagic) scavengers.
On the other end of the scale are various, minute water fleas, shrimp, and even tinier copeopods. Throughout the Subphylum generally, complexity is pretty much the same with variations for the enviornments and habits of some animals. All fit into their niches well, but few can survive out of them. Aracnids are a different kettle of, well, er, not-fish. Many are still very 'primitive' and others are quite 'advanced.'
"The Spider Web of Evolution
The order Araneae (spiders) is traditionally divided into three divisions; the Mesothelae (also known as the Liphistomorpha), the Mygalomorphae, tarantulas and relatives (also called the Orthognatha or the Theraphosomorphae) and the Araneomorphae, the rest of the spiders (also known as the Labidognatha). However it is possible the Mesothelea are really a part of the Mygalomorphae, this would leave us with only two groups; the primitive Tarantula types (Mygalomorphae) and the more advanced Aranaeid type (Araneomorphae).
If you have got this far I am very proud of you, that was an awful lot of very big words, it doesn't matter if you can not pronounce them all. The important thing is that we have two groups of spiders, one of which we call 'primitive' and the other 'advanced'. The 'primitve' Orthognathans have chelicera (fangs) that flex up and down, i.e. they bite wholly vertically, while the 'advanced' Labidognathans have chelicera that flex sideways i.e. they bite at least partly, horizontally or down and inwards at the same time."
I'm proud of you too. Some of them words was real sciencey, wasn't they? But again, we see the limitations of the exosleleton. All arthropods of any considerable size are aquatic crustations.
I could go on through other aracnids, insects, millipedes, and so forth, but these will give the picture I'm trying clumsely to get across. These guys had five hundred, million years to become what they are today, and they accomplished it way ahead of schedual. They are truely complex and very well fit into their niches, but can that complexity continue to increase in light of their exoskeletons?
This is not to sat that they will no longer continue to evolve; they certainly will and are even as we speak. But evolution does not need to build complexity to create a successful species. A mantis shrimp is vastly different in form and habit from a harlequin shrimp, but it is no more complex.
 
Evolution does not have to 'advance' but merely adapt a creature to survive and reproduce. Crustations are very good at both, but I don't see where they'll evolve to be anything but what they already are. Unless their enviornment changes to the point of where it would be advantageous to replace the exoskeleton (with what?), and that seems unlikely even for such a blind & screwed-up process as evolution.
The long and short of it is that they got it right not too long after the beginning, geologically speaking, and needed little more complexity beyond species diversification.
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"What luck for rulers that men do not think." -- Adolf Hitler (1889 - 1945)
"If only we could impeach on the basis of criminal stupidity, 90% of the Rethuglicans and half of the Democrats would be thrown out of office." ~~ P.Z. Myres
"The default position of human nature is to punch the other guy in the face and take his stuff." ~~ Dude
Brother Boot Knife of Warm Humanitarianism,
and Crypto-Communist!
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Dr. Mabuse
Septic Fiend
Sweden
9687 Posts |
Posted - 03/19/2008 : 12:58:30 [Permalink]
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The more base-pairs an organism has, the more mutations that organism will experience per cellular division.
Having a damn lot of base-pairs (or chromosomes for that matter) allows for a greater storage-potential of genetic mutations.
This is a train of thought I've been nurturing for some time now (since my astro-biology studies):
Genetic Drift have been mentioned as a major competitor for evolution of a species against plain simple survival of the fittest after a mutation event.
But consider that mutations goes anywhere in the genome, even recessive genes. This way, a species builds up a number of what I'd describe as sleeping mutations. Once there is a major change in the environment these mutations can manifest themselves as positive traits thanks to sexual recombination of the genome. Suddenly the species have the opportunity to explode into a new environment.
Sexual recombination of genes is a practically instant (within a generation or two) means of adapting compared to plain mutation-vs-selection pressure.
More DNA simply means grater storage potential for sleeping mutations. More DNA usually also means more complex organism.
Just take a look at canines. They have an even bigger genome than we do. Are they more complex? I can't say, I'll have to defer to a biologist. But breeding them has showed a remarkable potential for diversity. Once breeders reach the outer limits of what sexual recombination can express of the mutations that are stored within the genome, we get inbreeding. Dogs that can't give natural birth to its offspring, bad backs, etc.
Leaving them there, at the edge, they will have to start relying on plain, new mutations for their continual development.
A Chow-Chow and a Grand Danes are unlikely to breed so even leaving a few packs of them close to each other, we have a huge potential for a speciation event.
This is just my own ranting though. Feel free to disagree.
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Dude
SFN Die Hard
USA
6891 Posts |
Posted - 03/19/2008 : 13:25:42 [Permalink]
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| Assuming the evidence is accurate and generally holds true for other groups then how can that be explained? |
If accurate, it indicates that complexity as they define it,
"But instead they found organisms that developed increasingly complicated structures and characteristics."
... confers a survival benefit.
Perhaps "complicated structures and characteristics" allow for adaptation to a wider range of environmental variables?
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-- Thomas Jefferson
"god :: the last refuge of a man with no answers and no argument." - G. Carlin
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HalfMooner
Dingaling
Philippines
15831 Posts |
Posted - 03/20/2008 : 13:35:50 [Permalink]
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Often, complexity simply makes for better efficiency. Though some organisms indeed do better by discarding unneeded complexity in favor of simplicity that works in their niches, others have built upon a long history of incrementally beneficial mutations that add up to greater complexity.
A new post by PZ Myers illustrates this, with the near-universal example of the ATPase molecular machine. This "device" uses proton-powered rotation to cause special protein factories to make ATP molecules, the power-plants of life in the bodies of everything from bacteria to Sally Kern.
But this remarkable machine wasn't created whole: Scientists have shown that a mutated, much simpler version of it still rotates correctly. That simple version may resemble the original form of this "engine." But that simpler version is much less efficient than the more complex, evolved version that is today present almost universally in life.
Evolution doesn't "care" for complexity, nor for simplicity. It is simply a principle of survival, and anything that works is passed to descendants. Complexity is sometimes the path to efficiency.
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“Biology is just physics that has begun to smell bad.” —HalfMooner
Here's a link to Moonscape News, and one to its Archive. |
| Edited by - HalfMooner on 03/20/2008 13:41:58 |
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Evolution Favors Complexity Over Time?
